High performance engines require quick response times. The drive transmissions must shift speeds quickly to provide optimum performance. This is particularly true in racing situations, for example in snowmobile racing.
The infinitely variable drive pulley for belt drive transmissions commonly found in snowmobile engines is well known. A key part of the clutch system in those transmissions is the actuator lever or shifter which operates as a cam relative to a fixed roller by pivoting about a pivot point on an axially moveable sheave so that in response to centrifugal force the axially moveable sheave of the system is urged towards an axially fixed sheave.
Pulleys of this type typically comprise opposed frusto-conical flanges which co-operate with a drive belt. The cone pulley is secured axially on the shaft and the other can be moved axially against the force of a return spring, by centrifugal weights in the form of adjusting levers that act on an adjusting stop through a cam surface and which are each supported so as to be able to pivot outwards about a pin that extends transversely to the shaft and is spaced radially therefrom.
The size of the V-gap between the two pulley flanges of such drive transmissions is a function of the particular rotational speed. It is known that levers acting as centrifugal weights can be associated with the axially adjustable pulley flange, these levers being supported on rollers associated with the fixed flange, so that when the adjusting levers pivot outwards as a result of centrifugal force the axially moveable flange is pressed towards the fixed flange. The axial adjustment path of the pulley thus depends on the angle to which the adjusting levers are pivoted, which in turn is determined by centrifugal forces and by the shape of the rolling track for the rollers on the adjusting levers.
Thus, for a given course of the return force, a desired inter relationship of the axial movement of the movable flange and the rotational speed can be achieved by the shape of the rolling track of the adjusting lever (which forms a cam surface) and by the mass of the centrifugal weight formed by the adjusting lever, and the position of the centre of gravity of such mass. However, a given relationship between the axial movement of the moveable flange and the rotational speed can only be maintained if the position of the cam surface of the adjusting lever and the mass of the centrifugal weights and the position of the centre of gravity of such weights can be kept within close tolerances. It is extremely difficult to guarantee this in components made by production, and requires subsequent adjustment work.
It is known that to adjust the weighted levers, the position of each lever or of the roller that is associated with it as an adjustable abutment can be moved. However, such a step provides a corresponding matching potential and adjustment only in the range of small adjustment paths but not, however, in the range of larger adjustment paths, for which a match would be of considerably greater importance.
Representative of the art is U.S. Pat. No. 5,326,330 which discloses an infinitely variable drive pulley for a belt drive transmission with two flanges arranged on a shaft and which accommodate a V-belt. One flange is fixed axially on the shaft and the other is moveable in the axial direction against the force of at least one return spring by centrifugal weights in the form of adjusting levers. The adjusting levers each acts on an abutment cam surface, and is supported so as to be able to pivot out about a pin that extends transversely to the shaft, spaced radially therefrom. The adjusting levers can be moved relative to their pivot pins through an adjustment eccentric.
What is needed is a CVT having an eccentric collar having an indexing portion, the indexing portion engagable with the receiving portion on the CVT body, the indexing portion engaging the receiving portion to lock the eccentric collar and thereby pivot shaft in a desired position with respect to the axis of rotation of the CVT. The present invention meets this need.